Functional expression of the particulate methane mono-oxygenase gene in recombinant Rhodococcus erythropolis

In order to construct an expression system for the particulate methane mono-oxygenase (pMMO) gene (pmo), the structural gene cluster pmoCAB amplified from Methylosinus trichosporium OB3b was inserted into a shuttle vector pBS305 under the control of a dsz promoter and transformed into Rhodococcus erythropolis LSSE8-1. A stable transformant was successfully obtained using ethane as the sole carbon source. Fluorescence in situ hybridization results showed that the dsz promoter allowed the pmo genes to be transcribed in the recombinant strain. The effects of Cu²⁺ and Zn²⁺ concentrations on cell growth and pMMO activity in ethane-containing medium were examined. It was discovered that 7.5 μM Cu²⁺ and 1.8 μM Zn²⁺ were suitable to achieve high cell concentration and pMMO activity, but the amount of methanol accumulated during methane oxidation by the recombinant strain was still low.